diff --git a/tcms/testplans/views.py b/tcms/testplans/views.py
index 8557b7d323..3cc217f5f9 100644
--- a/tcms/testplans/views.py
+++ b/tcms/testplans/views.py
@@ -208,7 +208,8 @@ def get_context_data(self, **kwargs):
 
     def get_form(self, form_class=None):
         form = super().get_form(form_class)
-        form.populate(self.object.product_id)
+        product_id = self.request.POST.get("product", self.object.product_id)
+        form.populate(product_pk=product_id)
         return form
 
     def get_form_kwargs(self):